This disclosure relates to connection diagnostics for parallel speakers.
Conventional automotive audio systems are equipped with circuits that test the connection state of the connected electroacoustic transducers, i.e., speakers, in the system. Such systems typically apply a current and measure whether the impedance on the line is above or below a threshold indicative of the presence of the intended speaker. If the speaker is missing, the impedance will be too high. If the speaker connection is short circuited, the impedance will be too low. These techniques can also detect whether either of the conductors going to the speaker is shorted to power or to ground.
It is also typical in automotive audio systems to connect two speakers, such as a mid-range speaker or woofer, and a tweeter, in a parallel configuration on a single output line of an amplifier. A woofer will reproduce low-frequency components of a broadband audio signal, the tweeter will reproduce the high-frequency components of the same total signal, and a mid-range speaker will reproduce signals in-between the ranges of the woofer and tweeter. Typically, one or the other of a woofer and a mid-range speaker will be paired with a tweeter in the sorts of systems discussed herein. Note that by “woofer,” “mid-range,” and “tweeter” we refer simply to any two speakers suited to two different bands of audio, without intending to specify any particular crossover frequency. The diagnostic techniques mentioned above, as currently employed, cannot accurately determine the connectivity of both speakers in a pair of speakers connected in parallel.